This invention relates to coating type magnetic recording media having a magnetic layer containing a hexagonal crystal plate magnetic powder. More particularly, it relates to improvements in the runnability and recording density of disk-shaped magnetic recording media having a hexagonal crystal plate magnetic powder contained in the magnetic layer.
In recent years, a great demand for high density recording is imposed on magnetic recording media for the purposes of increased recording capacity and size reduction. Conventional commonly used magnetic recording media are coating type media because of productivity and many other advantages, and most of them have a magnetic layer containing needle magnetic powder such as gamma-Fe.sub.2 O.sub.3 and cobalt coated gamma-Fe.sub.2 O.sub.3. Magnetic recording media having such magnetic powder contained, however, have a certain limit with respect to recording density.
One approach toward a high recording density is a perpendicular recording method which utilizes the residual magnetization of a magnetic recording medium in a direction perpendicular to the surface of the medium. Known among such perpendicular magnetic recording media is a magnetic recording medium having a hexagonal crystal plate magnetic powder such as barium ferrite and strontium ferrite contained in its magnetic layer (see Japanese patent application Kokai No. 57-195328). These perpendicular magnetic recording media offer a higher recording density particularly when a magnetic powder having a reduced particle size is used. However, disk-shaped media utilizing such very finely divided magnetic powder are insufficient in runnability during their operation. Generally, the disk-shaped media are electrically charged by friction due to high speed rotation during their operation, and such frictional charging is one of the factors of prohibiting runnability improvement.